1. Field of the Invention
The present invention relates to a map search-and-display method for capturing the positioned relationship between two points at a predetermined distance from each other and obtaining detailed maps showing the two points and areas therearound. The present invention further relates to a map display apparatus for performing the above-described method. The above-described method and apparatus may be used in a navigation apparatus.
2. Description of the Related Art
For example, general navigation systems include a map-and-information data recording medium storing map data for drawing a map and facility-information data for searching a facility or the like. The map-and-information data recording medium can be a CD-ROM, a DVD-ROM, a hard disk, and so forth. Typical navigation systems further include a data capture device for capturing data of the map-and-information data recording medium, a display device for displaying a map or the like, and a vehicle-position detection device for detecting the current position and travel direction of a vehicle by using a self-contained navigation device including a GPS receiver, a running-distance sensor, and a gyrocompass. Subsequently, it becomes possible to capture map data including the vehicle current position from the map-and-information data recording medium, draw the image of a map showing areas around the vehicle current position on a screen of the display device based on the captured map data, display a vehicle-position mark on the display screen, scroll the map image according to the vehicle movement, and fix the map image on the screen and move the vehicle-position mark, so as to understand where the vehicle is located at a glance.
The map data stored in the map-and-information data recording medium is separated by a suitable longitude width and a suitable latitude width according to various scale levels. Data on a road or the like is stored, as a cluster of coordinates of nodes represented by longitudes and latitudes. The road data includes at least two connected nodes, and the map data includes a road layer having a road list, a node table, an intersection-forming node list, and so forth, a background layer for displaying a road, a building, a facility, a park, a river, and so forth, on the map image, and information data for displaying characters, map symbols, and so forth, of an administrative-tract name such as the names of a city, a town, and a village, the road name, the intersection name, the facility name, and so forth.
Further, the navigation systems have a route-guidance function so that a user can easily travel toward a predetermined destination or a passing spot (hereinafter referred to as an destination) without taking a wrong road. According to the route-guidance function, it becomes possible to set the destination by using various units that will be described later and calculate and propose a suitable route fulfilling various requirements from among routes linking a starting point with the destination. Further, it becomes possible to store the data on a route selected by the user, as guidance-route data, and display the guidance route, as a thick line of color different from that of lines of other roads, on the image map during traveling. Further, where the distance between the vehicle and an intersection where the vehicle should change its travel direction on the guidance route becomes shorter than a predetermined distance, the intersection is enlarged, an arrow mark or the like indicating the changed travel direction is displayed, and speech guidance on right or left turn is provided. Subsequently, it becomes possible to guide the user to the destination.
In the case of the above-described navigation systems, it is necessary to set the destination to which the vehicle travels at the current position where the vehicle starts traveling. For setting the destination, the address of the destination is inputted directly. However, the destination address is inputted according a guidance image, where the guidance image gradually changes from a wide-area name to a narrow-area name. Further, the phone number of a predetermined facility or the like stored in the map-and-information data recording medium with the location information thereof is inputted, so as to search a map showing a point where the predetermined facility exists. Otherwise, information of the predetermined facility is narrowed down according to a genre and an area, so as to search the map showing the point where the predetermined facility exists.
According to the above-described method for searching a destination, the user must remember the address of a predetermined point correctly for searching for the predetermined point by address. However, where the user does not remember the address correctly, it takes significant time and many procedures for searching the predetermined point. Further, even though inputting the phone number of the predetermined point is an easy method for searching for the predetermined point, this method is useless for searching a map showing a facility whose phone number is unknown or an area other than areas around a facility whose phone-number data is known.
However, a map-scroll search method performed by moving a cursor is widely used, as a map-search method that can be performed easily and smoothly by the user. According to this method, the cursor is displayed on a screen and moved from the current position displayed on the screen by using a remote control or the like, whereby a map displayed on the screen is scrolled in all directions. Further, the scroll speed is arbitrarily adjusted by detecting the cursor movement and the scale of the map is changed, as required.
The map-scroll search method performed by moving the cursor will be described as below. First, as shown in FIG. 15A, a current-position centered map on a first detailed scale, which is the most detailed scale of all, is displayed, for example. The user starts scrolling the map for performing a cursor-moving map search process. In this process, the user moves the cursor for setting a destination and displays and designates a predetermined point on the map, as the destination. Subsequently, a cursor-position centered map is displayed on the screen at all times. As a result, the cursor is fixed on the screen center and the map moves in a reverse direction, as shown in FIG. 15B. Therefore, the current position gradually moves in a direction reverse to the cursor moving direction, whereby a new map centered on the cursor regarded by the user is displayed continuously.
Accordingly, where the cursor is moved in the arrow direction, as shown in FIG. 15B, the current position often disappears from the screen, as shown in FIG. 15C. As a result, the current position is not displayed on the screen and only the cursor position is displayed on the screen center, as shown in FIG. 16A. Where the cursor is moved up and down, or from side to side on the above-described screen, it becomes difficult to know the current-position direction and the distance between the current position and the cursor position. In this case, the user changes from the first detailed scale to a predetermined scale for a wide-area map for displaying an area wider than the area shown in the map on the first detailed scale, so as to display the current position on the screen.
However, where the cursor is moved to a predetermined point distant from the current position, as shown in FIG. 16A, and the user wishes to display the current position and the cursor position on the same screen, it is often insufficient to change the first detailed map scale to the next detailed map scale, that is, a second detailed map scale. That is to say, the user often has to change the map scale several times for displaying a wider area map.
Because it is troublesome to repeat the above-described process for performing the cursor-moving map search, the applicant of the present invention has proposed a technology disclosed in Japanese Unexamined Patent Application Publication No. 2002-286467. According to this technology, where the current position is disappearing from the screen, as shown in FIG. 15C, it becomes possible to display a map on a predetermined scale for displaying the cursor position and the current position on the same screen automatically, without changing the cursor position on the screen center regarded by the user on the currently-displayed map, as shown in FIG. 16B. The map is calculated based on data including the distance between the current position and the cursor position, the map-scale rate, the screen size, and so forth. FIG. 16B shows an example where the detailed scale is changed from the first detailed scale to the next detailed scale for displaying a wider area, that is, the second detailed scale.
According to the above-described technology, the current position can be displayed on the screen all the time irrespective of how the cursor is moved by the user. Subsequently, the cursor-moving map search process can be performed easily. However, where the cursor is moved away from the current position, a new map showing a wider area than the map on the second detailed scale is displayed, as shown in FIG. 16C. The scale of the new map is referred to as a third detailed scale. In the case of the map on the third detailed scale, however, only main roads are displayed in areas around the current position and the cursor position. Therefore, it is difficult to see the real road status around the current position and the cursor position by observing the map on the third detailed scale.
For example, where the user tries to find a predetermined convenience store on a predetermined point by scrolling a map showing an excessively wide area, the name of the predetermined point is often not displayed. Particularly, the predetermined convenience store is not displayed in most cases. Therefore, where it is estimated that the predetermined point is near the cursor position, the user changes the map scale manually, so as to display a new map on a more detailed scale than that of the currently displayed map. Then, the user determines whether or not the point or the convenience store exists by searching the new map. Where neither the point nor the convenience store exists on the map screen, the above-described operations are repeated, so as to perform a search for a predetermined map repetitively.
As has been described above, the relationship between the current position and the cursor position is clearly understood by displaying the map showing the two positions on the same screen. However, because the map shows a wide area, it becomes difficult to obtain detailed map information for the two positions. This problem is not limited to the case where the two positions are displayed during the map is searched by moving the cursor. For example, where a search is made for a facility, the position relationship between the facility and the current position is confirmed through a map displayed on the same screen. However, where the user wishes to obtain a detailed map for the facility, a detailed map for areas around the facility, a detailed map for the current position, and a detailed map for areas around the current position, the above-described problem also occurs. According to the known map display method, the map showing the current position and a searched facility is displayed and the map is switched to a detailed map centered on a facility to be searched. Further, display operations including a step of displaying a detailed map centered on the current position by moving the cursor, for example, need to be repeated.
Further, where the user is going to use a highway and wishes to select an interchange for entering the highway from an ordinary road, or an interchange for going from the highway to the ordinary road, a predetermined interchange is displayed. However, where the user wishes to make a search for an interchange more suitable than the first interchange, based on a highway route map, the user wants to see a highway route map displaying the first interchange and the more suitable interchange for understanding the position relationship between the two interchanges and a detailed map for understanding the ordinary-road status around each of the interchanges. In this case, according to the known map-display method, it becomes necessary to switch between a highway route map on a suitable scale and a detailed map showing the ordinary-road status around each of the interchanges by performing many display operations.